1. Technical Field
The present invention relates to a proximity sensor using a magnetic field to detect the presence or absence of a metal body as an object to be detected or to detect the position of the metal body.
2. Related Art
A proximity sensor using a magnetic field is known as one of sensors detecting the presence or absence of a metal body as an object to be detected or detecting the position of the metal body. This proximity sensor is widely utilized mainly for various production facilities, industrial robots and the like.
The proximity sensor mainly includes a cylindrical housing, a coil assembly having a core and a detecting coil, and a circuit board provided with a processing circuit electrically connected to the detecting coil. The coil assembly is disposed at the front end within the housing. In addition, at least a part of the circuit board provided with the processing circuit is disposed behind the coil assembly within the housing.
In recent years, the proximity sensor is often provided with a light emitting device as an indicator light. This light emitting device as an indicator light includes, for example, a device turning on/off the light in accordance with turning on/off of the power supply, a device turning on/off the light in accordance with the detection state of the metal body, a device turning on/off the light in order to inform the user of the information used for making various settings when the proximity sensor is installed, and the like.
When used in any of the above-described cases, the light emitting device as an indicator light is generally mounted on one of the main surfaces of the circuit board provided with the processing circuit as described above. For example, Japanese Patent Laying-Open No. 11-312446, Japanese Patent Laying-Open No. 2007-35583 and the like disclose a proximity sensor in which a light emitting device as an indicator light is mounted on one of the main surfaces of the circuit board.